Sodium Indicators
Sodium indicators allow spatial and temporal resolution of Na+ concentrations in the presence of physiological concentrations of other monovalent cations. These sodium indicators exhibit an increase in green fluorescence emission intensity upon binding Na+, with little shift in wavelength. Creative Biolabs provides Sodium indicators with optional fluorophore in cell permeant or impermeant formats for worldwide customers.
Sodium Indicators at a Glance
There is a major difference in the sodium ion concentration outside and inside the cell. The Kd values for intracellular and extracellular are 5-40 mM and 120-450 mM, respectively, depending on the organism. This concentration gradient is extremely important for nutrient uptake, to regulate concentrations of other intracellular ions and solutes, and to generate and transmit electrical impulses in excitable cells. The low intracellular sodium concentration requires the use of sensitive dyes able to register any small variation. Two major functions of sodium indicators include:
- Measure steady-state changes in Na+ concentration
- Track Na+ bursts in axons and presynaptic terminals
How to Choose Optimal Sodium Indicators?
1. Since intracellular potassium concentration is typically higher than sodium (in excess of 100 mM), Na+ indicators should respond selectively to Na+, not K+.
2. The TMA salt is the water-soluble and membrane impermeant salt form of sodium indicators available for calibration purposes or for invasive loading, such as microinjection into cells or loading through a whole-cell patch electrode, as well as for in vitro calibration of the dye.
3. The acetoxymethyl (AM) ester form of sodium indicators is non-invasive and is the most popular method for loading fluorescent ion indicators into cells. These esters make the molecule hydrophobic enough to be membrane permeant. Once inside the cell, non-specific esterases found in almost all cell types, hydrolyze the esters back to the polyanionic form necessary for water-solubility, retention in the cell, and sensing ions.
Our Sodium Indicators are Available To
1. Estimate Na+ gradients in isolated mitochondria
2. Measure intracellular Na+ levels
3. Measure Na+ efflux in cells
4. Correlate changes in intracellular Na+ with Ca2+ and Mg2+ concentrations, intracellular pH, and membrane potential in combination with other fluorescent indicators.
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